Response surface modelling of <scp>CO<sub>2</sub></scp> capture by ammonia aqueous solution in a microchannel
Pourya Asgarifard, Masoud Rahimi, N. Tafreshi
Abstract
Abstract Post‐combustion CO 2 capture is one strategy of greenhouse gases mitigation. Ammonia is a useful option as CO 2 absorbent and an alternative to conventional amine‐based solutions. This study deals with CO 2 capture by ammonia aqueous solution in a co‐current two‐phase flow by utilizing a T‐shaped microchannel. Three parameters of temperature, gas flow rate, and ammonia concentration were considered as the main parameters affecting the CO 2 capture efficiency. A response surface methodology based on central composite design (CCD) was used to model the CO 2 capture efficiency as output in terms of the aforementioned input variables. CCD suggested a quadratic model to fit the experimental data. The model validation was implemented by ANOVA. All statistic tools including correlation coefficient, P ‐value, and F‐value of the model, and P ‐value of lack‐of‐fit confirmed that the prediction model was significant. It was deduced from F‐values that the importance of the input variables followed the sequence of ammonia concentration > gas flow rate > temperature. Ammonia concentration was the most effective input variable because there was a direct correlation between ammonia concentration and the number of absorption sites in the liquid phase. Numerical optimization predicted the best output of 96.48% CO 2 capture under the following optimum conditions: temperature of 20.00°C, gas flow rate of 110.59 mL/min, and ammonia concentration of 0.1382 mL/mL (13.82 vol%). The average CO 2 capture of 95.42% obtained at the input conditions indicates the accuracy of the prediction model.